1. Field of the Invention
The invention relates in general to the field of integrated circuits, and, more particularly, o signals sent between integrated circuits. Specifically, the invention relates to a high frequency input buffer used to receive a signal from an integrated circuit.
2. Description of the Related Art
Integrated circuits are small electronic devices that are generally made in a semiconductor material and classified by the number of transistors and other electronic components that they contain. Numerous integrated circuits can be used in a simple device, such as a computer, audio equipment, video equipment, etc. With growing complexity of electronic devices, there has been a corresponding growth in the size and complexity of the integrated circuits contained therein. In fact, complex electronic devices, such as computers, now contain millions of transistors arranged into many integrated circuits.
When multiple integrated circuits are being used within one type of device (e.g., a microprocessor), it may become beneficial to have communication (i.e., the sending and receiving of electronic signals) between the circuits. Typically, input buffers are used within the receiving integrated circuit to isolate the input signal from the remainder of the circuit. Conventional input buffers may employ an amplifier with an external feedback mechanism as shown in FIG. 1.
The differential amplifier 100 includes the input terminals 105 and 110 and an output terminal 115. The feedback mechanism for this differential amplifier 100 includes a resistor 120, which is connected external to the differential amplifier 100 between the output terminal 115 another resistor 130 between the negative terminal 125 and the input terminal 110. Conventional external feedback mechanisms may be problematic in that they draw current from or deliver current to a reference voltage. Owing to the large number of connections between integrated circuits, numerous input buffers are often needed within a semiconductor device. Due to the large number of input buffers connected to the reference voltage, the reference voltage may be altered.
Additionally, conventional input buffers have a preamplifier with a single output resulting in difficulty with amplifying small signals (e.g., 50 mV) to generate full swing (e.g., 1.5 V) high-frequency output signals (e.g., 800 Mhz) in the presence of noise.
Thus, it would be beneficial to have a high-frequency input buffer that is capable of overcoming the shortcomings of conventional methods.